// DBOS 演示程序
// 展示 Cz Exokernel + Safe Rust DBMS 的集成

const std = @import("std");
const dbos_mod = @import("dbos");

pub fn main() !void {
    std.debug.print("\n=== DBOS Demo ===\n", .{});
    std.debug.print("Database Operating System\n", .{});
    std.debug.print("Cz Exokernel + Safe Rust DBMS\n\n", .{});
    
    var gpa = std.heap.GeneralPurposeAllocator(.{}){};
    defer _ = gpa.deinit();
    const allocator = gpa.allocator();
    
    // 配置 DBOS
    const config = dbos_mod.DBOSConfig{
        .memory_size = 64 * 1024 * 1024,  // 64MB
        .disk_path = "dbos.db",
        .network_port = 5432,
        .max_connections = 100,
    };
    
    std.debug.print("Initializing DBOS...\n", .{});
    std.debug.print("  Memory: {d} MB\n", .{config.memory_size / (1024 * 1024)});
    std.debug.print("  Disk: {s}\n", .{config.disk_path});
    std.debug.print("  Port: {d}\n", .{config.network_port});
    std.debug.print("  Max Connections: {d}\n\n", .{config.max_connections});
    
    // 初始化 DBOS
    var dbos = try dbos_mod.DBOS.init(allocator, config);
    defer dbos.deinit(allocator);
    
    std.debug.print("✓ Exokernel initialized (TCB)\n", .{});
    
    // 启动 Safe Rust DBMS
    std.debug.print("Starting Safe Rust DBMS...\n", .{});
    try dbos.start_dbms();
    std.debug.print("✓ DBMS started (Safe Component)\n\n", .{});
    
    // 演示架构
    std.debug.print("=== Architecture ===\n\n", .{});
    std.debug.print("┌─────────────────────────────────┐\n", .{});
    std.debug.print("│      Applications (SQL)         │\n", .{});
    std.debug.print("├─────────────────────────────────┤\n", .{});
    std.debug.print("│   Safe Rust DBMS (Untrusted)   │\n", .{});
    std.debug.print("│  • Query Parser                 │\n", .{});
    std.debug.print("│  • Storage Engine               │\n", .{});
    std.debug.print("│  • Transaction Manager          │\n", .{});
    std.debug.print("├═════════════════════════════════┤\n", .{});
    std.debug.print("│   Cz Exokernel (TCB ~1000 LOC) │\n", .{});
    std.debug.print("│  • Capability System            │\n", .{});
    std.debug.print("│  • Memory Management            │\n", .{});
    std.debug.print("│  • Disk I/O                     │\n", .{});
    std.debug.print("├─────────────────────────────────┤\n", .{});
    std.debug.print("│         Hardware                │\n", .{});
    std.debug.print("└─────────────────────────────────┘\n\n", .{});
    
    // 演示查询（模拟）
    std.debug.print("=== Example Queries ===\n\n", .{});
    
    const queries = [_][]const u8{
        "CREATE TABLE users (id INT, name TEXT)",
        "INSERT INTO users VALUES (1, 'Alice')",
        "INSERT INTO users VALUES (2, 'Bob')",
        "SELECT * FROM users WHERE id = 1",
        "UPDATE users SET name = 'Charlie' WHERE id = 2",
        "DELETE FROM users WHERE id = 1",
    };
    
    for (queries) |query| {
        std.debug.print("SQL> {s}\n", .{query});
        
        // 模拟执行
        const result = try dbos.execute_query(query);
        _ = result;
        
        std.debug.print("  ✓ Executed (0 rows affected)\n\n", .{});
    }
    
    // 性能优势
    std.debug.print("=== Performance Advantages ===\n\n", .{});
    std.debug.print("✓ Zero-copy I/O\n", .{});
    std.debug.print("  Traditional: App → DB → OS → Disk (3 copies)\n", .{});
    std.debug.print("  DBOS:        App → DBMS → Exokernel → Disk (0 copies)\n\n", .{});
    
    std.debug.print("✓ Custom Memory Management\n", .{});
    std.debug.print("  DBMS controls page eviction policy\n", .{});
    std.debug.print("  No OS interference\n\n", .{});
    
    std.debug.print("✓ Direct Hardware Access\n", .{});
    std.debug.print("  Bypass OS layers\n", .{});
    std.debug.print("  Minimal latency\n\n", .{});
    
    // 安全保证
    std.debug.print("=== Security Guarantees ===\n\n", .{});
    std.debug.print("✓ Minimal TCB (~1000 lines)\n", .{});
    std.debug.print("  Easy to audit and verify\n\n", .{});
    
    std.debug.print("✓ Memory Safety\n", .{});
    std.debug.print("  Safe Rust compiler guarantees\n", .{});
    std.debug.print("  No use-after-free, no double-free\n\n", .{});
    
    std.debug.print("✓ Capability System\n", .{});
    std.debug.print("  Fine-grained access control\n", .{});
    std.debug.print("  Unforgeable capabilities\n\n", .{});
    
    std.debug.print("=== Demo Complete ===\n", .{});
}
